The present invention relates to a device for releasable connecting an interface with test equipments.
Testers such as IC testers are provided for generating dedicated analog and/or digital signals to a device under test (DUT) and analyzing the response thereof. Such testers are described in detail e.g. in the co-pending European patent application No. 99105625.0 by the same applicant, EP-A-88299, U.S. Pat. No. 5,499,248 or U.S. Pat. No. 5,453,995.
In most cases, the provision of signals from the tester to a specific application site of the DUT has to be matched with the specific mechanical and electrical properties of the tester as well as of an application equipment handling the DUT.
FIG. 1 shows an example of a typical DUT application equipment such as a wafer prober 10 for transporting and positioning highly sensitive silicon wafers as DUTs. The wafers (not visible inside the wafer prober 10) are internally connected to a probe card 20 as interface of the wafer prober 10 towards a tester 25 (in FIG. 1 only symbolized as a general block). Wafer probers are generally applied for testing integrated circuit in the earliest possible production phase.
The probe card 20 is typically a device-specific printed circuit board (PCB), e.g. with high-density contact needles on the wafer side and gold-plated contact pads on the tester side (as the side visible in FIG. 1). The probe card 20 normally straddles the dense (needle) pattern from the wafer side to a wider pad pattern for contacting the tester 25. The size of the probe card 20 is generally limited by the hardware of the wafer prober 10. The wafer prober 10 has to ensure a reliable electrical contact between the contact pads of the wafer and the probe card 20.
A load board 30 represents the electrical and mechanical interface of the tester 25 towards the DUT. The Load board 30 normally is a device specific printed circuit board (PCB) custom-built for the specific requirements of the DUT application equipment and can be exchanged dependent on the respective application. More details about the load boards 30 are described in particular in the aforementioned copending European patent application No. 99105625.0. In case that the load board 30 is provided as a custom-built exchangeable part, the load board 30 is often contacted within the tester 25 by means of spring-loaded contact pins (also called “Pogo™”).
While the load board 30 and the probe card 20 are electrically optimized (e.g. with respect to signal speed, signal purity, impedance, and transmission rate) regarding either the tester 25 or the DUT of the wafer prober 10, a good electrical and mechanical matching between the load board 30 and the probe card 20 has to be achieved. This becomes in particular important with increasing signal transmission rates going up to two Gigabit per second.
In the example of FIG. 1, an interface tower 50 (also called “Pogo™ tower”) is used as interface between the load board 30 and the probe card 20. The interface tower 50 converts the pin pattern (normally rectangular arrangement) of the load board 30 of the tester to the pattern (normally round and more dense) of the probe card 20. In the example of FIG. 1, the interface tower 50 further has to bring signals from the tester 25 through a round-shaped hole in a head plate of the wafer prober 10 and bridge the spatial distance between the load board 30 and the probe card 20.
All the interfacing provided by the interface tower 50 has to be done with a minimum loss in performance for the entire test system provided by the tester 25 and the application equipment of the wafer prober 10. That means, that all parts in the electrical path of the interface tower 50 have to maintain a controlled impedance (normally 50 Ω) and a high contact quality for each provided tester channel (e.g. more than 1.000 channels).
The interface tower 50 comprises rods for adjusting and fixing the interface tower 50 to different load boards 30. The load boards 30 are fixed by screw connections.
To ensure the high contact quality it is requested, that the mechanical and electrical contact between the interface tower and the load board is after each change of load board of the same condition. Therefore all screw connections have to be tighten up properly to achieve the required mechanical and electrical contact between the interface tower and the Load board. A visual control is not possible given. The screw connections are furthermore very time consuming for changing load boards.